Mitosis and Cell Cycle Study Guide

Outline the stages and events of interphase

• G₁

• S

• G₂

G₁ Phase

Cell Growth and differentiation

S Phase

Synthesis and replication of chromosomes

G₂ Phase

Synthesis of molecules other than DNA, needed for cell division

Brainstorm a list of 3 metabolic reactions that might occur in each phase of interphase

• G₁: Phosphorylation of glucose, polymerization of tubulin or actin, sub-pho of ATP in cytoplasm

• S: Polymerization of DNA, translation of histone mRNAs, actions of all the DNA replication machinery

• G₂: Phosphorylation of ADP, synthesis of microtubule components, cyclin synthesis

Name the phase of mitosis and label the diagram with the following terms: Chromosomes, centrioles, centromere, kinetochore microtubules, polar microtubules, telomeres, chromatids

Phase of mitosis: Probably prometaphase

Define the role of the mitotic spindle in mitosis

The mitotic spindle separated chromatids by attaching fibers to the kinetochores of the chromosomes. These chromosomes then end up in separate daughter cells.

Prophase in an animal cell w/ the chromosome number of 6 (2N = 6)

• Chromosomes condense

• Mitotic spindle grows out of the centrosomes

• Kinetochore appears at the centromeres

• Centrosomes migrate towards the poles

Prometaphase in an animal cell w/ the chromosome number of 6 (2N = 6)

• Nuclear envelope disintegrates

• Kinetochore appears at the centromere of each chromatid

• Spindle fibers attach to the kinetochore

Metaphase in an animal cell w/ the chromosome number of 6 (2N = 6)

• The centromere-kinetochore complexes align in the equator of the cell

Anaphase in an animal cell w/ the chromosome number of 6 (2N = 6)

• Chromatid disjunction (chromatids are pulled apart)

• DNA molecules move towards opposite poles

Telophase in an animal cell w/ the chromosome number of 6 (2N = 6)

• Nuclear envelope reforms

• Spindle disappears

• DNA reverts to chromatin

• Nucleolus reforms

Cytokinesis in Plant Cells

• Cell plate formation using vesicles

• New cell wall forms between the two nuclei

Cytokinesis in Animal Cells

• Cleavage furrow formation because of contractile ring microfilaments

• Cell membrane pinches between 2 nuclei and splits apart

Cytokinesis similarities in both plant AND animal cells

• Results in 2 identical daughter cells

• Occurs directly after telophase

• Divides cytoplasm

• Separates 2 nuclei

Why are cleavage furrows absent in plant cells?

The presence of the cell wall, which is rigid and not very bendable, in plant cells prevents the cell from forming cleavage furrows

Predict 3 molecules you would expect to find at or near the cell plate in a plant cell

• Phospholipid in vesicle

• Cellulose

• Membrane proteins

The mechanical control of the cell cycle is regulated at molecular level by a cyclically operating set of molecules. Cyclins and cyclin-dependent kinases (CDKs) are proteins that control a cell’s passage through the cell cycle. The CDKs are present at a constant level in the cell. How is their kinase controlled?

CDK binds to cyclin and P group. Transfers P group to activate target protein. Loss of P groups leads to cyclin degradation

What evidence suggests that CDK is a kinase?

It transfers a phosphate group

Metastasis/ What happens when cancer cells metastasize?

Metastasis: Where individual cancer cells break away and start a new tumor somewhere else

Distinguish between a benign and malignant tumor.

• Benign: Tumor doesn’t invade surrounding tissue

  • Not spreading so it’s non-cancerous

• Malignant: Tumor is invading surrounding tissue

  • It is spreading so it’s cancerous

Since many cells undergo apoptosis, why don’t cancer cells also undergo apoptosis?

Damage or change in genetic material of these cells leads to changes in gene expression and metabolism that result in cancer cells ignoring cell signals to undergo apoptosis

Oncogene genes

Codes for a protein that stimulates cell division, found in cancer cells

Tumor suppressor genes

Regulates cell division, reducing likelihood of unchecked cell division and formation of tumors

What are the contrasting actions between oncogene and tumor suppressor genes?

Oncogenes stimulate cell division, while tumor suppressor genes slow it down